Electronic-parts mounting board and electronic-parts mounting board frame

ABSTRACT

An electronic-parts mounting board frame sheet includes a plurality of electronic-parts mounting board frames serially coupled into a single sheet. Each frame includes an electronic-parts mounting board with an insulating substrate, grouped leads protruding from the insulating substrate, an outer frame integrally formed with the grouped leads, and pilot holes, located in the outer frame, for indicating the positions of the grouped leads of the electronic-parts mounting board. Further, the grouped leads and the outer frame of each electronic-parts mounting board frame are integrally formed.

This application is a continuation-in-part of U.S. patent applicationSer. No. 797,032, filed Nov. 25, 1991.

BACKGROUND OF THE INVENTION

1 . Field of the Invention

The present invention relates to an electronic-parts mounting board, andan electronic-parts mounting board frame with a plurality ofelectronic-parts mounting boards assembled thereinto.

2. Discussion of the Related Art

Various types of electronic-parts mounting boards have been proposed.One of those known electronic-parts mounting boards is anelectronic-parts package, or a semiconductor device. In the package,after an electronic part is mounted on the board, the board is entirelycovered for sealing purposes with a so-called resin mold, while theouter leads of the semiconductor device protrude outwardly from theresin mold.

An electronic-parts mounting board sealed with a resin mold is disclosedin Japanese Patent Laid-Open Publication No. Sho. 59-98545, entitled"Pellet Mounting Board," which is for a semiconductor device. Thepublication claims a part or "pellet" mounting board "wherein a pelletis mounted on a pellet mounting board with a conductive layer, bondingpads of said pellet are electrically connected to said conductive layerby a wire bonding method, and said conductive layer of said pelletmounting board is bonded to a lead frame." The disclosed pellet mountingboard suffers from the following problems, however:

1) Solder is used for bonding the pellet mounting board (referred to asa board) to the conductive layer. Each portion (pad) subjected to thesoldering lies on an insulating board. Accordingly, the pad tends topeel off the insulating board when it is heated for soldering.

2) The insulating board is located between the pads. Solder mistakenlyleft on the insulating board possibly may cause an electrical shortbetween the pads.

3) The thermal expansion coefficient of the board is different from thatof the lead frame. When the pellet (electronic part) is heated, the leadframe tends to peel off the board. One possible cause of the peel-off iswarping of the lead frame.

4) The major surfaces of the insulating board do not fully utilize thespace available to form the conductive circuits.

To cope with the above problems, an electronic-parts mounting board hasbeen proposed which is constructed such that an insulating board isapplied to both sides of the lead frame, to form a one piececonstruction, and the conductive circuits on the insulating board areelectrically connected to the leads through the through-holes.

To be more specific, the proposed mounting board uses lead frames eachhaving leads, connected by tie bars, that are constructed such thatinner leads are electrically connected to the conductive circuitsthrough the through-holes, and outer leads protrude from both theinsulating board and the resin mold and are physically continuous.

The electronic-parts mounting board thus constructed still involvesunsolved problems, however, as follows:

5) In recent usage of the electronic-parts mounting board, a pluralityof electronic-parts mounting boards are assembled into a frame, in orderto routinely and efficiently mount electronic parts on the board and toseal the structure with a resin mold. To assemble the insulating boardbased electronic-parts mounting boards into the lead frame, a singlemetal plate is punched to form leads in the locations where a pluralityof electronic-parts mounting boards are to be formed. Insulating boards,separately formed, are coupled with the leads.

6) In the electronic-parts mounting boards thus assembled into oneframe, if a part of the lead frame is defective, the whole lead framemust be treated as being defective. Accordingly, the remainingnon-defective parts of the lead frame are wasted. The portions of thelead frame to be used for the electronic-parts mounting boards requireespecially delicate working for their formation. The cost to form thoseportions is higher than that to form other portions. Therefore,replacement of only those portions to be used for the electronic-partsmounting boards with non-defective portions would be very advantageous.

7) Since a plurality of electronic-parts mounting boards are assembledinto a single lead frame, the whole lead frame must be individuallydesigned and manufactured so as to have a shape in conformity with theshape of the electronic-parts mounting boards. In this respect, theversatility of the lead frame in usage is poor.

8) The electronic-parts mounting board must be subjected to electricalchecks or tests in the stages of manufacturing the board. Simplificationof the process of subjecting the board to electrical testing would behighly advantageous.

Studies made by the inventors to solve the above problems and to reducethe disadvantages of the electronic-parts mounting board have resultedin the present invention.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstancesand has as an object the provision of an electronic-parts mounting boardand an electronic-parts mounting board frame in which, when a part ofthe board and the board frame is defective, only the defective part needbe replaced with a nondefective one, thereby providing a high productionyield, high reliability, and low cost.

Another object of the invention is to provide an electronic-partsmounting board and an electronic-parts mounting board frame in whichsimplified electrical testing may be accomplished during manufacture.

An additional object of the invention is to provide an electronic-partsmounting board and an electronic-parts mounting board frame in whichonly a defective part need be replaced and in which handling and framingof the boards is simplified.

Yet another object of the invention is to provide an electronic-partsmounting board having a standardized inner lead frame and a mountingboard frame with integral but separate, and therefore easily customized,outer lead frames for electrical connection with the standardized innerlead frame.

A final object of the invention is to provide an electronic-partsmounting board frame which is high in reliability and production yield,and in which the exact position of a pilot hole relative to a relatedgroup of leads is maintained.

To achieve the above objects, the invention preferably provides anelectronic-parts mounting board frame constructed such that a pluralityof electronic-parts mounting boards are assembled into a single frame,wherein a plurality of leads formed in each electronic-parts mountingboard are formed from a member discrete from the member constituting theframe, and are electrically connected to the frame.

In the preferred electronic-parts mounting board frame, a plurality ofelectronic-parts mounting boards are separately formed. Those boards areassembled into a frame by means of leads. Therefore, a defectiveelectronic-parts mounting board, may be replaced with a non-defectiveboard without wasting other non-defective boards.

According to another aspect of the invention, there is provided anelectronic-parts mounting board frame constructed such that a pluralityof electronic-parts mounting boards are assembled into a single frame,wherein a plurality of leads for each electronic-parts mounting boardinclude outer leads integral with the frame and inner leads formed of adiscrete member separate from the frame and the outer leads, aninsulating board is applied to both sides of the inner leads such thatthe inner leads protrude from the insulating board and the protrudinginner leads are electrically connected to the outer leads, whereby theplurality of electronic-parts mounting boards are assembled into theframe. Thus, in this preferred electronic-parts mounting board frame,the leads include the inner leads to which the insulating board isapplied, and the separate outer leads to be connected to the inner leadsprotruding from the insulating board. More specifically, the inventionpreferably includes an inner lead frame in which the inner leads areconnected by tie bars, and an outer lead frame including outer leadswhich are integral with the frame, the inner and outer lead frames beingelectrically connected by, for example, soldering.

According to still another aspect of the invention, there is provided anelectronic-parts mounting board frame constructed such that a pluralityof electronic-parts mounting boards are assembled into a single mountingboard frame, wherein a plurality of electronic-parts mounting boards areassembled into the mounting board frame, to form a one-piececonstruction in such a manner that an insulating board is applied toboth sides of the lead frames, each lead frame including an individuallyformed outer frame which is fixed to the mounting board frame.

In this variation of the inventive electronic-parts mounting boardframe, the outer frame is provided on the peripheral side of the leadsto which the insulating board is applied. When the plurality of theelectronic-parts mounting boards are assembled into one mounting boardframe, the outer frame of each electronic-parts mounting board is fixedto the mounting board.

To achieve the final object of the invention, there is provide anelectronic-parts mounting board frame sheet having a plurality ofelectronic-parts mounting board frames each including anelectronic-parts mounting board with an insulating substrate, groupedleads protruding from the insulating substrate, an outer frame, andpilot holes located in the outer frame for indicating positions of thegrouped leads on the electronic-parts mounting board. In a preferredembodiment of the electronic-parts mounting board sheet, a plurality ofelectronic-parts mounted board frames are serially coupled into a singlesheet.

According to this embodiment of the invention, the grouped leads and theouter frame of the electronic-parts mounting board frame are integrallyformed. Further, the plurality of electronic-parts mounting board framesto be coupled preferably includes only non-defective frames selectedfrom among pre-manufactured electronic-parts mounting board frames.

In order to facilitate coupling, end parts of the electronic-partsmounting board frames which make up the sheet are formed with astep-shape. When the electronic-parts mounting board frames are coupledtogether, the stepped end parts of one electronic-parts mounting boardframe is placed on a stepped end part of an adjacent electronic-partsmounting board frame, and then bonded together by spot welding.

Thus, in this final embodiment, a plurality of electronic-parts mountingboard frames, each including an electronic-parts mounting board, areserially coupled together to form an electronic-parts mounting boardframe sheet having a series of electronic-parts mounting board framesselected from among non-defective manufactured ones. As a result, theelectronic-parts mounting board frame sheet thus formed is especiallyreliable. If the product of the electronic-parts mounting board framesheet is damaged during subsequent processing steps, only the damagedelectronic-parts mounting board frame need be replaced with anondefective one. Replacement is facilitated by the use of the discretemounting board frames. This leads to an improvement in the productionyield of the electronic-parts mounting board frame sheet.

Further, the outer frame and the grouped leads of the electronic-partsmounting board frame are integrally formed. The outer frame containspilot holes formed therein. When the electronic-parts mounting boardframe sheet is subsequently processed, no distortion is transmitted to arelated group of leads, thereby ensuring an exact positionalrelationship of the pilot hole to the related grouped leads.

BRIEF DESCRIPTION OF THE DRAWINGS

A The accompanying drawings, which are incorporated in and constitute apart of this specification illustrate embodiments of the invention and,together with the description, serve to explain the objects, advantagesand principles of the invention. In the drawings,

FIG. 1 is a plan view showing an electronic-parts mounting board frameaccording to a first embodiment of the invention;

FIG. 2 is a plan view showing in enlarged fashion how eachelectronic-parts mounting board is coupled with a frame;

FIG. 3 is a plan view showing an electronic-parts mounting board frameaccording to a second embodiment of the invention, the illustrationtypically showing one electronic-parts mounting board in connection witha frame;

FIG. 4 is a plan view showing an inner lead frame of theelectronic-parts mounting board used in the electronic-parts mountingboard frames of FIG. 3;

FIG. 5 is a plan view showing the inner lead frame when an insulatingboard is applied to the lead frame, and tie bars are removed from thelead frame;

FIG. 6 is a plan view showing one of outer lead frames 13 with which theelectronic-parts mounting board shown in FIG. 5 is to be coupled;

FIG. 7 is a diagram showing one of the coupling modes when the innerlead portions of the electronic-parts mounting board are connected tothe outer lead portions of the outer lead frame, the illustrationtypically showing the connection of one inner lead portion to one outerlead portion, for simplicity;

FIGS. 8 and 9 are diagrams showing additional coupling modes;

FIG. 10 is a longitudinal sectional view showing in enlarged fashion asemiconductor device using the electronic-parts mounting board of theelectronics-parts mounting board frame according to the secondembodiment;

FIG. 11 is a partial plan view showing an electronic-parts mountingboard frame according to a third embodiment of the invention;

FIG. 12 is a sectional view taken on line XII--XII in FIG. 11;

FIG. 13 is a partial, enlarged plan view showing a modification of theelectronic-parts mounting board frame according to the third embodiment;

FIG. 14 is a sectional view taken on line XIV--XIV in FIG. 13;

FIG. 15 is a sectional view showing another connection of the outer leadportions of the frame to the inner lead portions of the leads 11, theillustration showing typically one outer lead portion and the inner leadportion;

FIG. 16 is a partial, enlarged plan view showing an additionalmodification of the connection of the frame and the outer lead frame inthe third embodiment;

FIG. 17 is a longitudinal sectional view showing a semiconductor deviceconstructed using the electronic-parts mounting board of FIG. 1;

FIG. 18 is a sectional view showing a further connection of the innerand outer lead portions; and

FIG. 19 is a sectional view showing another connection of the frame 20and the outer frame 31.

FIG. 20 is a plan view showing an electronic-parts mounting board framesheet which constitutes another embodiment of the invention.

FIG. 21 is a cross-sectional view showing two electronic-parts mountingboard frames coupled into an electronic-parts mounting board framesheet.

FIG. 22 is a plan view showing an electronic-parts mounting board withgrouped leads used in the electronic-parts mounting board frame of FIG.20.

FIG. 23 is a cross-sectional view showing an electronic-parts mountingboard with grouped leads.

FIG. 24 is a vertical sectional view showing a semiconductor deviceconstructed using the electronic-parts mounting board of FIG. 23.

FIG. 25 is a plan view showing an electronic-parts mounting board frameused in the electronic-parts mounting board frame sheet of FIG. 20.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate an electronic-parts mounting board frame 100according to a first preferred embodiment of the present invention. Asshown therein, four electronic-parts mounting boards 10 are mounted on asingle frame 20, to form a single unit. In each electronic-partsmounting board 10, an insulating board 14 is applied to the inner sidesof groups of leads 11, and the inner sides of the boards and the leadsgroups are unified into a single piece construction. As shown in FIG.10, conductive circuits 15 formed on the insulating board 14 areselectively and electrically connected to the grouped leads 11 throughthroughholes 16. The respective leads 11, as shown in FIG. 2, protrudefrom the insulating board 14. The electronic-parts mounting board 10,which is to be assembled into the electronic-parts mounting board frame100, may be completed as a semiconductor device 200, after an electronicpart 40 is mounted thereon. In this case, as shown also in FIG. 17, theend faces of a mold resin 50 thereof are positioned on the leads 11.Thus, the frame 20 is used only for supporting each electronic-partsmounting board 10 by means of the leads 11. In the semiconductor device200 as shown in FIGS. 10 and 17, the frame is not used.

The frame 20, as shown in FIG. 1, is a plate-like member with a numberof holes 5 for receiving the electronic-parts mounting boards 10. Withthe shape of the frame as illustrated, the frame 20 has a rigidity highenough not only to support the electronic-parts mounting boards 10 butalso to allow the frame itself to be transferred to a mounting apparatusfor mounting the electronic parts 40 and a transfer mold apparatus forthe mold resin 50.

The electronic-parts mounting boards 10 are mounted on the frame 20 insuch a manner that the leads 11 , as shown in FIG. 2, are connected attheir tips to the frame 20 by suitable means, such a spot welding orsoldering, for example. In this instance, to connect the leads 11 to theframe 20, the leads 11 are directly placed on the frame 20, as shown inFIG. 2. Alternatively, the tips or ends of the leads may abut againstthe frame as shown in FIG. 14 or the half-etched ends of the leads maybe coupled with the half-etched edge of the frame as shown in FIG. 15.

In the electronic-parts mounting board frame 100 thus constructed, whichis the first embodiment of the invention, a plurality ofelectronic-parts mounting boards 10 are assembled into one frame 20 andfixed thereto by means of the grouped leads 11. With this construction,if one of the electronic-parts mounting boards 10 is defective, thedefective board may be replaced with a non-defective one, while theremaining ones may be used as they are. The electronic-parts mountingboard frame 100 is of course constructed so as to provide for efficientmounting of the electronic part 40 and to seal the substantially wholeelectronic part 40 within the mold resin 50, as shown in FIG. 10 or 17.

The electronic-parts mounting board frame 100 includes two separatemembers; one member is for the leads 11 for the electronic-partsmounting boards 10, and the other is for the frame 20 for supporting theelectronic-parts mounting boards 10. As a result, the cost ofmanufacture of the electronic-parts mounting board frames 100 is reducedbecause the simpler structure members, i.e., the frames 20, and the morecomplicated members, such as leads 11, may be separately manufactured.Furthermore, the cost to manufacture the semiconductor devices 200 usingthe electronic-parts mounting boards 10 is also reduced. When the boardsare used for the semiconductor devices 200, the frames 20 are not used.Those frames may be used later, if required.

The electronic-parts mounting boards 10 are individually manufactured asproducts having the leads 11. Therefore, those boards can beelectrically tested board by board. The leads when electricallyseparated as shown in FIG. 2, may also be tested in a simple manner leadby lead.

A second embodiment of an electronic-parts mounting board frame 100according to the invention will be described with reference to FIGS. 3to 10. In this embodiment of frame 100, the leads 11 for connecting theelectronic-parts mounting board 10 to external components or devices areeach divided into two portions, an inner lead 11a and an outer lead 11b.The jointed portions of the inner and outer leads 11a and 11b aredisposed within the mold resin 50, when the electronic-parts mountingboards 10 are completed as the semiconductor devices 200, as shown inFIG. 10. In the figures, a single electronic-parts mounting board 10 andits related parts are illustrated for simplicity. The frame 20 islocated outside an outer lead frame 13 integral with groups of outerleads 11b. A plurality of outer lead frames 13 are assembled into asingle frame 20, to form a single unit.

FIG. 3 is a plan view showing one of the electronic-parts mountingboards 10, which are to be assembled into an electronic-parts mountingboard frame 100 according to the present invention. An insulating board14 including conductive circuits 15 is disposed in the central part ofthe board. The outer leads 11b of the leads 11 protrude from theinsulating board 14. The leads 11 of the board 10 are constructed suchthat the inner leads 11a of an inner lead frame 12 are electrically andphysically connected to the outer leads 11b of the outer lead frame 13,respectively, by suitable means, such as by soldering.

For forming the electronic-parts mounting boards 10, a plurality ofinner lead frames 12 as shown in FIG. 4 and a plurality of outer leadframes 13 as shown in FIG. 6, which are assembled into the frame 20, areprepared. The inner lead frames 12 and the outer lead frames 13, whichare assembled into the frame 20, are separately manufactured. The frame12 shown in FIG. 4 is formed by punching or etching out of a metal plateinner leads 11a, which are connected by means of tie bars 12a. The metalplate is made of a material such as 42 alloy or copper compositematerial. An insulating board 14 on which conductive circuits 15 havebeen formed or are to be formed, is applied to the central part to forma unit, as shown in FIG. 5, in which the inner leads 11a are caused toprotrude from the insulating board 14. The protrusion of the inner leads11a is made because the inner leads 11a must be coupled with the outerleads 11b in later manufacturing steps. In the inner lead frame 12 shownin FIG. 4, a terminal 11c which will serve as a base terminal or groundterminal is formed in the central part toward which the inner leads 11aare extended. Preferably, some of the inner leads 11a are connected to acentral terminal 11c. The central terminal 11c is, however, notessential to the invention.

As shown in FIG. 10, necessary conductive circuits 15 are formed on theinner lead frame 12 with the insulating board 14 applied thereto asshown in FIG. 5, and through-holes 16 are formed therein to electricallyconnect the conductive circuits 15 to the inner leads 11a. In the innerlead frame 12, both sides of which are covered with the insulating board14, the tie bars 12a which tie the inner leads 11a together are cut off,for example, by a press machine, as shown in FIG. 5. As a result,although the inner leads are each electrically connected to theconductive circuits 15 on the insulating board 14 through thethrough-holes 16, they nevertheless protrude separately from theinsulating board 14.

Let us consider the lead frames 13 which are assembled into the frame20. Typically, in one outer lead frame 13, as shown in FIG. 6, the outerleads 11b are connected by tie bars 13a, the lead frame being punchedout of a metal plate made of 42 alloy or copper composite material, forexample. In the illustrated example, the number of inner leads 11a ofthe inner lead frame 12 is equal to the number of outer leads 11b of theouter lead frame 13. However, if required, the numbers of leads need benot equal to each other. For example, where the electronic-partsmounting board is used as a semiconductor device 200, the number ofouter leads 11b of the outer lead frame 13 need only be that requiredfor the semiconductor device 200.

In assembling the electronic-parts mounting board frame, the outer leadframes 13 thus constructed are positioned so that the end faces of theouter leads 11b respectively confront the end faces of the inner leads11a of the inner lead frame 12. Then, those leads are electricallyconnected by soldering, for example, and the tie bars, 13a, which arenow unnecessary, are cut off for removal by well known means. Finally,the electronic-parts mounting boards 10 each as shown in FIG. 3 areformed. In this case, the inner leads 11a and the outer leads 11b may beconnected by using

a) solder as just mentioned,

b) conductive adhesive,

c) anisotropic conductive rubber, or

d) any other suitable connection means.

If any of those is used, the connecting work is performed while securingthe electrical conduction therebetween.

In connecting leads 11a and 11b, the lead shapes may be varied,providing beneficial effects. For example, the outer leads 11b may berelatively fat as shown in FIG. 7, to increase their rigidity. The leads11a and/or 11b may also be shaped so as to have enlarged circular tips,as shown in FIG. 8. The enlarged circular tips are suitable for moresecurely holding solder or adhesive. Additionally, the tips of the leadsmay be apertured as shown in FIG. 9. With the apertured tips, solder oradhesive is even more securely held, increasing adhesive strength.Further, as shown in FIG. 18, the tips of the leads 11a and 11b may behalf etched to form stepped parts. The stepped parts of the leads arelaid one upon the other for coupling purposes as shown in FIG. 18. Inthis case, the jointed portion of the leads thus coupled have smoothedsurfaces.

As already stated, in manufacturing a plurality of inner lead frames 12and a plurality of outer lead frames 13 assembled into the frame 20,both frames making up the electronic-parts mounting board frame 100, ametal plate is formed into predetermined patterns by a suitable means,such as by punching. For example, a single metal plate may be punched toform the inner lead frames 12 and the outer lead frames 13. That is, anumber of lead frames may be punched out of a single metal plate. Inthis case, the punching work is applied separately to the inner leadframes 12 and the outer lead frames 13. This simplifies theirmanufacture, and improves the efficiency of the manufacturing operation.In the instant embodiment, 150 inner lead frames 12 were punched out ofa 1/6 square meter copper plate. 42 outer lead frames 13 correspondingto the inner lead frames 12 were punched out of a 1/8 square meter42-alloy plate.

The electronic-parts mounting board frame 100 thus constructed ismanufactured in the following manner: The insulating board 14 is pressedon both sides of each inner lead frame 12, so that those are combinedinto a single unit. Necessary components, e.g., conductive circuits 15,and through-holes 16 are formed on and in the structure. Thereafter, thetie bars 12a are cut off to form the inner leads 11a, which are causedto independently protrude form the insulating board 14. Then, theelectrical connection of the inner leads 11a to the conductive circuits15 through the through-holes 16 is checked for each of theelectronic-parts mounting boards 10, and the electronic-parts mountingboards having defective electrical connections are removed. Thenon-defective electronic-parts mounting boards 10 are thus selected and,as shown in FIG. 3, assembled into the outer lead frames 13 which havebeen assembled into the frame 20.

An electronic part (e.g., a semiconductor element) 40, as shown in FIG.10, is mounted on one or both sides of the insulating board 14 of eachelectronic-parts mounting board 10. The electronic part 40 and theconductive circuit 15 are electrically connected by a bonding wire 41.Finally, the structure is entirely sealed with mold resin 50 thuscompleting, in this example, an intended semiconductor device 200.

The electronic-parts mounting boards 10 making up the electronic-partsmounting board frame 100, in the second embodiment of the invention, maybe used for forming the semiconductor device 200, as shown in FIG. 10.To form the board, the electronic part 40 is mounted on theelectronic-parts mounting board 10. The structure is entirely sealedwith the mold resin 50, in a state in which the outer leads 11b extendoutwardly. The electronic-parts mounting boards 10 thus formed areassembled into the frame 20 by using the leads 11, as shown in FIG. 1.An additional embodiment to be described later employs an assembly inwhich a plurality of outer leads 11b of each electronic-parts mountingboard 10 are assembled into a single frame 20, and in which theelectronic-parts mounting boards 10 are assembled into the frame 20 andfixed thereto by the leads 11 .

In the electronic-parts mounting board frame 100, the leads 11 , as alsoshown in FIG. 3, are formed by connecting the inner leads 11a and theouter leads 11b by means of solder, for example. As already stated, theleads 11a and 11b are formed of different members. The outer leads 11bare protected by the frame 20. Those leads 11a and 11b wheninterconnected are electrically continuous and are shaped to correspondto that of frame 20. Specifically, the electronic-parts mounting boardframe 100 is formed in such a way that the insulating board 14 isapplied to both sides of the inner lead frames 12 as shown in FIG. 4,thereby combining them into single units, and the single units areassembled into outer lead frames 13, as shown in FIG. 3, and the outerlead frames 13 are enclosed by the frame 20 as shown in FIG. 6.

In the structure shown in FIG. 5, after the tie bars are cut off,electrical tests are performed on the inner leads 11a and the conductivecircuits 15 coupled therewith, independently of the outer leads 11b. Theresult is that only non-defective inner lead frames 12 are used for theresultant electronic-parts mounting board frame 100. Therefore, theproduct quality, particularly the electrical performances, of the framesis improved in comparison with products in which the leads arecontinuous.

This fact also improves production yield in manufacturing theelectronic-parts mounting board frames 100. The inner leads 11a and theouter leads 11b coupled with the frame 20, which cooperate to form theleads 11 and tend to be defective, may be electrically testedindividually, before the electronic-parts mounting boards 10 containingthem are assembled. Therefore, the electronic-parts mounting boards 10assembled from those electrically tested leads 11a and 11b have muchfewer defects, providing an excellent production yield.

In accordance with the invention, the inner lead frames 12 and the outerlead frames 13 coupled to the frame 20 are formed of different discretemembers. Further, in forming the lead frames, increased tolerances forthe inner and outer leads 11a and 11b are possible. The number of leadframes that can be punched out of a metal plate of a fixed are is threetimes the number of lead frames in which the leads consist of physicallycontinuous inner and outer leads. For example, the present invention hasbeen made to achieve a yield of 900 pieces/square meter, while in thecase of continuous leads the maximum yield achieved was 336pieces/square meter.

The inner lead frames 12, each having a preset number of inner leads11a, are manufactured as standard products. In this case, the presentnumber of the leads 11a is preferably as large as possible. The outerlead frames 13 having the outer leads 11b protected by the frame 20 maythen be separately customized for different types of products. In thisway, the electronic-parts mounting board frame 100 itself can be readilystandardized while nevertheless permitting use in a variety of differentapplications. This is a very beneficial feature in view of recent markettrends calling for customized manufacture of small numbers of productsfor each of a variety of different applications.

In the semiconductor device 200 based on the electronic-parts mountingboard frames 100, the outer leads 11b not only extend outside the device200 but furthermore are designed to be directly connected to otherboards. Therefore, the outer leads 11b must be sufficiently rigid tosatisfy such usages. In the electronic-parts mounting board frame 100,different members are used for the inner lead frames 12 of the innerleads 1 la and the outer lead frames 13 of the outer leads 11b.Therefore, the member selected for the outer lead frames 13 may have ahigher rigidity than the member for the inner lead frames 12. Theelectronic-parts mounting board frames 100 may be designed so that theirouter leads 11b have satisfactorily high rigidity.

A third embodiment of an electronic-parts mounting board frame 100according to the present invention will be described with reference toFIGS. 11 to 17. In this embodiment, the electronic-parts mounting boards10 are assembled into the frame 20 by using a lead frame 30. The leadframe 30 is formed by unifying groups of leads 11 by means of an outerframe 31. To be more specific, to form the lead frame 30, grouped leads11 for the electronic-parts mounting board 10 are connected by means oftie bars. The external ends of the leads 11 are connected to the outerframe 31. An insulating board 14 is applied to both sides of the centralpart of the lead frame 30. Then, necessary conductive circuits 15 areformed on the structure, and through-holes 16 are formed in thestructure. The electronic-parts mounting boards 10 thus constructed, asshown in FIGS. 11 and 12, are each fixed to one frame 20 at theperipheral edge 31 of the lead frame 30.

As described above, in the embodiment shown in FIGS. 11 and 12, theelectronic-parts mounting boards 10 are assembled into the frame 20 byutilizing the outer frame 31 located at the tips of the leads 11. To fixframe 31 into frame 20, both sides of the outer frame 31 are placed onthe frame 20, and spot welded at the black points shown in FIG. 11 byresistance welding.

In this case, the inner side of the frame 20 and both sides of the outerframe 31 may be half etched in order to form steps, as shown in FIG. 19.When frames 20 and 31 are coupled, the stepped parts are laid one uponthe other. The jointed portions of the frame 20 and the outer frame 31have smoothed surfaces. With the smoothed surfaces of the jointedportions, the electronic-parts mounting board frame 100 may be easilypositioned in or on related devices as necessary. In this embodiment,the frame 20 and the lead frame 30 are both made of copper alloy.

A modification of the coupling of the electronic-parts mounting boards10 with the frame 20 is illustrated in FIGS. 13 and 14. In thismodification, as shown, both sides of the outer frame 31 have portions32 protruding therefrom. The inner sides of the frame 20 have indentedportions 21 shaped with U-shaped cross sections. When coupling the innerand outer frames, the protruding portions 32 of frame 31 are insertedinto the U-shaped indented portions 21 of frame 20, respectively, andare fixed by electron beams or seam welding. The electronic-partsmounting board 10 is automatically positioned with respect to the frame20 when the protruding portions 32 are inserted into the indentedportions 21. As a result, no stepped portions in the surface of theframe 20 are required. This provides a smooth positioning of theelectronic-parts mounting board frames 100.

The embodiment of FIG. 13 may be further modified as shown in FIG. 19.In this modification, the faces of the protruding portions 32 which areto be jointed, and the indented portions 21, are half-etched to bestepped as shown. For coupling the board with the frame, the steppedportions are laid one upon the other. As in the previous modification,no stepped portions are formed in the jointed portion of the protrudingportions 32 and the indented portions 21, providing for smooth framepositioning. The frame 20 and the lead frame 30 are both made of 42alloy.

A modification of the third embodiment of an electronic-parts mountingboard frame 100 according to the present invention will be describedwith reference to FIG. 16. In this modification, the lead frame 30 andthe frame 20 include, respectively a protruding portion 32 and anindented portion 21, as in the embodiment of FIG. 13. The protrudingportion 32, which protrudes from a location at the midpoint of the sideedge of the lead frame 30, is larger than the indented portion 21. Theprotruding portion 32 has a pilot hole 32a at the center. The pilot hole32a is used when the electronic-parts mounting board frame 100 istransferred and the frame per se is applied to a related device. Theprotruding portion 32, when located at the midpoint of the side edge ofthe lead frame 30, reliably positions the electronic-parts mountingboard 10 when work is applied to the board. The fact that the protrudingportion 32 is larger than the indented portion 21, results in easyrepositioning of the electronic-parts mounting board 10 in the frame 20.Spot welding by a YAG laser is applied to the overlapping portion of theprotruding portions 32 within the frame 20, to couple them. In thisembodiment, the frame 20 is made of copper ally, and the lead frame 30is made of 42 alloy.

As described above, in the electronic-parts mounting board frame 100according to the third embodiment shown in FIGS. 11 through 16, thegrouped leads 11 for each electronic-parts mounting board 10 are coupledtogether by the outer frame 31, to form the lead frame 30. The outerframe 31 of the lead frame 30 of each electronic-parts mounting board 10is assembled into the frame 20, to thereby form an electronic-partsmounting board frame 100. If one or more of the lead frames 30 of theelectronic-parts mounting boards 10 assembled into the electronic-partsmounting board frames 100 is defective, the board 10 containing thedefective lead frame 30 may be removed or replaced by a non-defectiveone. The remaining boards can be used as they are.

The conventional lead frame consists of a plurality of parts in order toform a number of electronic-parts mounting boards 10. On the other hand,in the present invention, the lead frames 30 for the electronic-partsmounting boards 10 are individually formed. In manufacturing the boards,the electronic-parts mounting board 10 experiences many manufacturingsteps. For example, an electronic part 40 is mounted on theelectronic-parts mounting board 10. To ease the manufacturing work, theouter frames 31 of the lead frames 30 of the electronic-parts mountingboard are assembled into a single frame 20, as shown in FIG. 1

As described above, the present invention brings about many beneficialfeatures.

In the electronic-parts mounting board frame 100 according to the firstembodiment, a plurality of electronic-parts mounting boards 10 areassembled into one frame 20 and fixed to the frame by grouped leads 11,to thereby form a single piece construction. If any of theelectronic-parts mounting boards 10 is defective, only the defective oneis removed and replaced with a non-defective one, while the remainingnon-defective boards are used as they are. Therefore, the cost tomanufacture the electronic-parts mounting board 100 is reduced.Electrical testing of the electronic-parts mounting boards 10 can beaccomplished before the electronic-parts mounting boards 10 areassembled into the frame 20. Therefore, the fixing work of the boards tothe frame is efficiently done, and the production yield of theelectronic-parts mounting board frames 100 is improved.

By assembling the electronic-parts mounting boards 10 into the frame 20,the electronic parts 40 may be efficiently mounted on theelectronic-parts mounting boards 10. Particularly if the frames 20 eachhaving a prescribed pattern are previously manufactured, theelectronic-parts mounting boards 10 may be routinely assembled using anautomated mounting device for mounting the electronic parts 40.Therefore, the electronic-parts mounting board frame 100 is especiallyconvenient when semiconductor devices 200 are formed by theelectronic-parts mounting boards 10.

In the electronic-parts mounting board frame 100, the leads 11 for eachelectronic-parts mounting board 10 include inner leads 11a and outerleads 11b. The inner leads 11a to which the insulating boards 14 areapplied, and the outer leads 11b integral with the frame 20, are formedof different members. Accordingly, the electronic-parts mounting boardframe 100 of this embodiment enjoys the same advantages as does thefirst embodiment. In particular, the inner lead frames 12, which aredifficult to manufacture and expensive, may be used for eachelectronic-parts mounting board 10. This allows only the non-defectiveelectronic-parts mounting boards 10 to be used for the electronic-partsmounting board frame 100. The result is to reduce the cost and improvemanufacturing yield of the resultant electronic-parts mounting boardframes 100.

Additionally, a number of the inner leads 11a and a number of the outerleads 11b, which make up the leads 11, may be previously manufactured.The conductive circuits 15 on the insulating board 14 are selectivelyconnected to the inner leads 11a, through the through-holes 16. Theelectronic-parts mounting boards 10 thus manufactured have an excellentversatility in usage.

In the electronic-parts mounting board frame 100 of the thirdembodiment, the lead frames 30 are previously manufactured for theelectronic-parts mounting boards 10. The lead frames 30 are assembledinto and fixed to the frame 20 by the outer frames 31, to thereby form asingle piece construction. Therefore, the third embodiment hasadvantages comparable with those obtained by the first embodiment.

Furthermore, in this embodiment, a number of leads 11 necessary for theelectronic-parts mounting board 10 are unified by each outer frame 31,to thereby form lead frames 30. The lead frames 30 thus formed areassembled into and fixed to the frame 20 by the outer frames.Accordingly, the lead frames 30 may be formed individually, leading tocost reduction.

The lead frames 30 may be connected to the frame 20 in such a mannerthat protruding portions of the lead frames 30 are inserted intoindented portions of the frame 20. In this case, the resultantelectronic-parts mounting board frame 100 is entirely flat in shape. Thepositioning of the electronic-parts mounting boards 10 to the frame 20is therefore simplified.

As seen from the foregoing description, the electronic-parts mountingboards 10 to be assembled into one frame 20 may be manufactured indifferent forms. This feature is very useful for the manufacture ofsmall volumes of customized products. When the electronic-parts mountingboards 10 are connected to the frame 20 by laying the half-etchedportions one upon the other, the resultant electronic-parts mountingboard frame 100 is planar in shape. The planar shape provides, forexample, for smooth positioning, of the electronic-parts mounting boardframe 100 on a mounting device for mounting electronic parts 40.

Finally, it will be understood by those skilled in the art that thephrase electronic-parts mounting board refers to a board on which eithera plurality of electronic parts or a single electronic part is mounted.The principles of the invention apply equally to either situation and itis consequently intended that the phrase electronic-parts mounting boardas used in the above description and the appended claims be construed tomean any board on which at least one electronic part would be mounted.

A preferred embodiment of an electronic-parts mounting board frame sheetaccording to the present invention will now be described with referenceto the accompanying drawing FIGS. 20-25.

FIG. 20 is a plan view showing an electronic-parts mounting board framesheet (hereinafter referred to as a frame sheet) 1100 according toanother preferred embodiment of the present invention.

A plurality of electronic-parts mounting board frames 1020 are seriallycoupled to form the frame sheet 1100. The board frame 1020, as shown inFIG. 25, includes an electronic-parts mounting board 1010 (FIGS. 22 and23), an outer frame 1021 connecting the outer end parts of groups leads1012 to fix them, and dam bars 1023, if required.

A copper plate is punched to form a lead frame 1024 with a patternhaving the groups of leads 1012, the outer frame 1021, and the dam bar1023. At this time, the pilot holes 1022, which are for indicating thepositions of the groups of leads 1012, are also formed in the outerframe 1021. Insulating substrates 1011 are thermally pressed on bothsides of the lead frames 1024 thus formed. Semiconductor circuits 1013,through-holes 1014, and the like are formed on the insulating substrates1011. In this way, an electronic-parts mounting board frame 1020 isformed.

A plurality of electronic-parts mounting board frames 20 thus formed areserially coupled together into an electronic-parts mounting board framesheet 1100. To couple the electronic-parts mounting board frames, theend parts of each board frame 1020, as shown in FIG. 2, are half-etchedto form a stepped end part. The stepped end part of one board frame 1020is placed on a stepped end part of the adjacent board frame 1020, andthe stepped end parts placed one upon the other are bonded together byspot welding to form spot welds 1030, for example. In the thus formedframe sheet 1100, the coupled portions of the board frames 20 havesmoothed surfaces, ensuring a smooth transfer of the frame sheet 1100when it is transferred.

In this embodiment, the stepped end parts of the board frames 1020 areused to couple the board frames 1020 together. Alternatively, the boardframes 1020 can be coupled in such a manner that the end face of oneboard frame 1020 abuts against the end face of another board frame 1020adjacent to the former, and under this condition welding, adhesive, oranother suitable coupling means is applied to the boundary part of thetwo adjacent board frames 1020.

As described above, the plurality of electronic-parts mounting boardframes 1020, as shown in FIG. 20, are serially connected together toform the electronic-parts mounting board frame sheet 1100. Preferably,only non-defective board frames 1020 are selected for the sheet fromamong a group of pre-manufactured electronic-parts mounting boardframes. Accordingly, the sheet 1100 does not contain any defectiveelectronic-parts mounting board frames and therefore is especiallyreliable.

When the frame sheet 1100 is transferred to subsequent process stagesand processed therein, it is possible that a board frame or board framesmay become damaged. If damaged, however, the defective one or ones needbe replaced with nondefective one or ones, without having to replace theentire sheet. Accordingly, the remaining board frames 1020 of the framesheet 1100 can still be utilized, avoiding waste of non-defective boardframes. This leads to improvement of the production yield.

The pilot holes 1022 are formed in the outer frame 1021 of each boardframe 1020. When the unnecessary outer frame 21 or a dam bar 1023 (FIG.25) are removed, the pilot holes 1022 are used for indicating thepositions of the groups of leads 1012. The outer frame 1021, dam bar1023, and grouped leads 1012 are integrally formed into a single pieceas the lead frame 1024. In the process step for the resin sealing, theboard frame 1020 is thermally expanded. In this case, no distortion iscreated between each pilot hole 1022 of the outer frame 1021 and therelated group of leads 1012. Therefore, the position of the pilot hole1022 relative to the grouped leads 1012 remains unchanged, providing anexact positional relationship between the pilot hole and the relatedgrouped leads.

The foregoing description of preferred embodiments of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings or may be acquired from practice of the invention. Theembodiments were chosen and described in order to explain the principlesof the invention and its practical application to enable one skilled inthe art to utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the claimsappended hereto, and their equivalents.

What is claimed is:
 1. In an electronic-parts mounting board frame sheethaving a plurality of electronic-parts mounting board frames, each frameincluding an electronic-parts mounting board with an insulatingsubstrate, grouped leads protruding from said insulating substrate, anouter frame, and means including pilot holes located in said outerframe, for indicating positions of said grouped leads on saidelectronic-parts mounting board, the improvement wherein said pluralityof electronic-parts mounting board frames are serially coupled into asingle sheet.
 2. An electronic-parts mounting board frame sheetaccording to claim 1, in which said grouped leads and said outer frameof each said electronic-parts mounting board frame are integrallyformed.
 3. An electronic-parts mounting board frame sheet according toclaim 1, in which said plurality of electronic-parts mounting boardframes comprise only nondefective frames selected from amongpre-manufactured electronic-parts mounting board frames.
 4. Anelectronic-parts mounting board frame sheet according to claim 1,wherein at least one end part of each said electronic-parts mountingboard frame is a step-shaped end part, and wherein a step-shaped endpart of one of said electronic-parts mounting board frames is situatedon a stepped end part of an adjacent one of said electronic-partsmounting board frames and bonded thereto.
 5. An electronic-partsmounting board frame sheet according to claim 4, wherein the step-shapedend parts of adjacent ones of said electronic-parts mounting boardframes are spot welded together.
 6. An electronic-parts mounting boardframe sheet according to claim 2, in which said plurality ofelectronic-parts mounting board frames comprise only nondefective framesselected from among pre-manufactured electronic-parts mounting boardframes,
 7. An electronic-parts mounting board frame sheet according toclaim 2, wherein at least one end part of each said electronic-partsmounting board frame is a step-shaped end part, and wherein astep-shaped end part of one of said electronic-parts mounting boardframes is situated on a stepped end part of an adjacent one of saidelectronic-parts mounting board frames and bonded thereto.
 8. Anelectronic-parts mounting board frame sheet according to claim 7,wherein the step-shaped end parts of adjacent ones of saidelectronic-part mounting board frames are spot welded together.